Sorbent masses for the chemical binding of harmful gases have become known from West German Offenlegungsschrift No. DE-OS 38,05,407. They are used to clean the breathing air in different ways and are used, e.g., in respirator filters carried by persons or in filters of ventilation systems. These sorbent masses consist, e.g., of active carbon acting as the carrier, which is provided with an impregnation consisting of copper oxide and alkali chromate.
In addition, the impregnation may also contain zinc compounds in the form of zinc oxide. Sorbent masses containing vanadates instead of chromates are also known. If, for example, copper carbonate and alkali vanadate are applied together to active carbon and cautiously heated, the copper carbonate is completely or partially decomposed, and a highly effective impregnation for binding acidic gases is formed. Instead of copper carbonate, it is also possible to use copper oxide or zinc oxide, which lead to the formation of copper oxide-alkali vanadate, and zinc oxide-alkali vanadate impregnations, respectively. To expand the scope of application of the sorbent mass to the binding of ammonia, it is also possible to add zinc chloride.
Such an impregnated filter meets the performance specifications of DIN 3181 for type B filters against acidic gases and type K filters against ammonia.
The prior-art sorbent masses have the disadvantage that chromium containing impregnations reduce the stability during storage and therefore must be overdimensioned in order have sufficient protective effect even after storage. This makes the filters bulky, which is disadvantageous especially in the case of escape devices.